Mmmmmm.......
Why not look at what's best for the job?
Petrol engines have a better power-weight ratio and have been proven over many years. The R101 which crashed at Beauvais in 1930 killing the Secretary of State for Air and the Director of Civil Aviation was an early example of the use of diesels.
Let me put it this way:-
We take an engine that was never designed to run on Jet Fuel and that has an inferior power-weight ratio to what is currently in use.
We take a fuel that was never designed for use in reciprocating engines.
We modify the engine to cope with the fuel. We don't modify the fuel at all.
Why do we do this?
Because it will make a more capable or safer aviation powerplant?
Or simply because the Tax Regime means Jet Fuel is cheaper?
I have difficulty in reconciling the idea that engineering gymnastics for the purpose of Tax Avoidance is a major advance in safety or efficiency.
One could argue that removing the cost differential contributes to safety.
Mike